System including reply signal that at least partially overlaps request

ABSTRACT

A system including a receiver and a transmitter. The receiver is configured to transmit a request. The transmitter is configured to transmit a reply signal that at least partially overlaps the request.

BACKGROUND

Typically, an electrical system includes a number of differentcomponents that communicate with one another to perform systemfunctions. The different components may be situated on the sameintegrated circuit chip or on different integrated circuit chips.Usually, an electrical system, such as the electrical system in anautomobile, includes one or more controllers, memory chips, sensorcircuits, and actor circuits. The controller digitally communicates withthe memory chips, sensors, and actors to control operations in theautomobile.

In digital communications a common time base is used to transmit andreceive data. The common time base needs to be provided to each of thecomponents and can be provided to each of the components via an explicitclock signal or by combining the time base with the transmitted data. Atransmitter transmits data via the common time base and a receiverreceives and decodes the data via the common time base. The receiveddata cannot be properly decoded without the common time base.

Another aspect of digital communications includes the start time of adata transmission. If the transmission start time is not coded on thecommon time base signal or in the data, another signal line is used toindicate the start of a data transmission. Many embedded systems includea common system clock and selection signals that select systemcomponents and indicate the start of data transmissions.

Often, in decentralized systems, a multi-wire communication system, suchas a serial peripheral interface (SPI), is used. Typically, a masterprovides a clock signal and a slave select signal to each component viaseparate signal lines. The master toggles the clock signal coincidentwith transmitted data and the slave select signals select components andindicate the beginning and/or end of a data transmission. In operationof an SPI system, the master configures the clock signal to a frequencythat is less than or equal to the maximum frequency of a slave and pullsthe slave's select line low. The master selects one slave at a time. Ifa waiting period is required, the master waits for the waiting periodbefore issuing clock cycles. During each clock cycle a full duplex datatransmission occurs, where the master sends a bit on one line and theslave reads the bit from the one line and the slave sends a bit onanother line and the master reads the bit from the other line.Transmissions include any number of clock cycles and when there are nomore data to be transmitted, the master deselects the slave and stopstoggling the clock signal.

Separate clock and select signal lines to each of the components can beused to provide bus ability. In addition, in these systems the masterscan send data to the slaves. However, separate signal lines increasecosts and manufacturers want to reduce costs.

To avoid using a separate clock line, the time base can be encoded intothe data. For example, Manchester encoding is a bit-synchronoustransmission method where data is transmitted bit by bit using a givenbit rate. In Manchester encoding, each bit is represented by either arising edge or a falling edge of an electrical signal, where the risingedge represents one of a logical one or a logical zero and the fallingedge represents the other one of a logical one or a logical zero.Between bits the electrical signal may need to transition to transferthe next bit and it is necessary to distinguish between edges thatrepresent bits and edges that are signal changes between bits. This isachieved by starting the transmission with a known bit sequence,referred to as a preamble. However, the preamble mechanism is for only aone-way transmission and the receiver is not able to control the starttime of the transmission. Also, the transmission requires twice thefrequency of the bit rate and high frequencies introduce electromagneticinterference (EMI) problems. In addition, dedicated circuits are needed,since it is difficult to encode and decode the data using typicalperipheral elements found on embedded controllers.

For these and other reasons there is a need for the present invention.

SUMMARY

One embodiment described in the disclosure provides a system including areceiver and a transmitter. The receiver is configured to transmit arequest. The transmitter is configured to transmit a reply signal thatat least partially overlaps the request.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

FIG. 1 is a diagram illustrating one embodiment of an electrical systemaccording to the present invention.

FIG. 2 is a block diagram illustrating a request signal and a replysignal in one embodiment of an electrical system.

FIG. 3 is a diagram illustrating a reply signal that is transmitted viaone embodiment of a transmitter.

FIG. 4 is a diagram illustrating one embodiment of an electrical systemthat includes a controller, a first sensor, and a second sensor.

FIG. 5 is a timing diagram illustrating the operation of one embodimentof the electrical system of FIG. 4.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments can be positioned in a number of differentorientations, the directional terminology is used for purposes ofillustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

It is to be understood that the features of the various exemplaryembodiments described herein may be combined with each other, unlessspecifically noted otherwise.

FIG. 1 is a diagram illustrating one embodiment of an electrical system20 according to the present invention. In one embodiment, system 20 ispart of an automobile's electrical system.

System 20 includes a receiver 22 and a transmitter 24. Receiver 22 iscommunicatively coupled to transmitter 24 via one or more communicationpaths at 26. In one embodiment, receiver 22 is part of one integratedcircuit chip and transmitter 24 is part of another integrated circuitchip. In one embodiment, receiver 22 and transmitter 24 are part of thesame integrated circuit chip. In one embodiment, receiver 22 is acontroller. In one embodiment, transmitter 24 is a sensor, such as anautomobile sensor. In one embodiment, transmitter 24 is an actor, suchas a relay circuit. In one embodiment, transmitter 24 is a controller.In other embodiments, receiver 22 and transmitter 24 are any suitablecomponents.

Receiver 22 transmits a request signal to transmitter 24 via one of thecommunication paths at 26 and transmitter 24 transmits a reply signal toreceiver 22 via one of the communication paths at 26. The reply signalincludes a synchronization signal that indicates the time base oftransmitter 24 and data. The request signal and the reply signal overlapin time, where at least a portion of the request signal occurs at thesame time as at least a portion of the reply signal. In one embodiment,the request signal and the synchronization signal overlap in time, whereat least a portion of the request signal occurs at the same time as atleast a portion of the synchronization signal.

Transmitter 24 transmits data correlated to the time base of transmitter24, where the length of the synchronization signal indicates the timebase of transmitter 24 and the length of each data signal representsdata bits. In one embodiment, each data signal represents a nibble ofdata, i.e. four data bits.

Receiver 22 receives the synchronization signal and measures the lengthof the synchronization signal to obtain the time base of transmitter 24.Based on the received time base, receiver 22 recovers data bitinformation from the data signals via measuring the length of the datasignals and comparing the measured length to the received time base oftransmitter 24. In one embodiment, the request signal includes a triggersignal and transmitter 24 starts the reply signal in response to thetrigger signal. In one embodiment, the request signal includes a triggersignal and transmitter 24 starts the synchronization signal in responseto the trigger signal. In one embodiment, the request signal includes atrigger signal and the length of the synchronization signal is measuredfrom the trigger signal to the end of the synchronization signalprovided via transmitter 24.

In one embodiment, receiver 22 transmits one or more commands and/ordata to transmitter 24 in the request signal. In one embodiment, therequest signal includes one or more transmitter identification values toselect one or more of multiple transmitters, which provides bus abilityin system 20. In one embodiment, the request signal includes datarequest parameters, such as sensor measurement range information thatdirects the transmitter to switch to a different sensor measurementrange or transmit data in the specified sensor measurement range. In oneembodiment, the request signal includes configurable parameters, such asrelay turn-on/off time that directs a relay to remain on/off for aspecified time. In one embodiment, the request signal includes commands,such as a self-test signal that directs the transmitter to perform aself-test or a memory test. In one embodiment, the request signalincludes a wake-up signal that powers up the transmitter from a sleepmode or power down mode. In one embodiment, the request signal includesa power down signal to power down the transmitter or put the transmitterin a power saving sleep mode. In one embodiment, the request signalincludes a send data and remain powered-up signal. In one embodiment,the request signal includes a send data and power down signal.

In one embodiment, receiver 22 transmits a request and transmitter 24transmits a pulse width modulated reply signal that includes asynchronization pulse followed by one or more data pulses. Thesynchronization pulse is the synchronization signal, where the length ofthe synchronization pulse represents the time base, i.e. clock speed, oftransmitter 24. Each of the data pulses represents one or more data bitsof information, such as transmitter status, transmitter data, andchecksum information. The request signal overlaps in time the pulsewidth modulated reply signal and the synchronization signal. Receiver 22receives the pulse width modulated reply signal and measures the lengthsof the synchronization pulse and the data pulses to recover data bitinformation.

Receiver 22 transmits the request via one of the communication paths 26and transmitter 24 transmits the reply signal via one of thecommunication paths 26. In one embodiment, receiver 22 and transmitter24 are communicatively coupled via one or more conductive lines, whereeach of the conductive lines is a communications path. In oneembodiment, receiver 22 and transmitter 24 are communicatively coupledvia one or more radio frequency (RF) frequencies, where each of the RFfrequencies is a communications path. In one embodiment, receiver 22 andtransmitter 24 are communicatively coupled via one or more opticalwavelengths, where each wavelength (color) is a communications path. Inone embodiment, receiver 22 and transmitter 24 are communicativelycoupled via magnetic signals. In one embodiment, receiver 22 andtransmitter 24 are communicatively coupled via pressure signals.

In one embodiment, receiver 22 transmits the request via onecommunications path and transmitter 24 transmits the reply signal viathe same communications path. In one embodiment, receiver 22 transmitsthe request via a first communications path and transmitter 24 transmitsthe reply signal via a second communications path.

Receiver 22 and transmitter 24 communicate to send a request signal fromreceiver 22 to transmitter 24 and a reply signal from transmitter 24 toreceiver 22. In other embodiments, receiver 22 is configured to send arequest signal from receiver 22 to transmitter 24 and a reply signalfrom receiver 22 to transmitter 24, and transmitter 24 is configured tosend a request signal from transmitter 24 to receiver 22 and a replysignal from transmitter 24 to receiver 22.

System 20 provides data communications between receiver 22 andtransmitter 24 via a single communications path, such as one conductiveline, or two communication paths, such as two conductive lines. Thesedata communications have a high tolerance to time base differencesbetween receiver 22 and transmitter 24. Also, the request signal and thesynchronization signal provide synchronization of the datacommunications and the request signal provides for the transmission ofcommands and/or data from receiver 22 to transmitter 24. In addition,the request signal can include transmitter identifications that can beused in communications from a receiver to multiple transmitters, i.e.bus ability.

FIG. 2 is a block diagram illustrating a request signal 50 and a replysignal 52 in one embodiment of system 20. Reply signal 52 includes asynchronization signal 54 and data signals 56. Synchronization signal 54is a time base signal that indicates the time base of transmitter 24.Each of the data signals 56 is correlated to the time base indicated viasynchronization signal 54.

Receiver 22 transmits request signal 50 to transmitter 24 via one of thecommunication paths 26 and transmitter 24 transmits reply signal 52 toreceiver 22 via one of the communication paths 26. In response to atrigger signal at 58 in request signal 50, transmitter 24 startssynchronization signal 54. After reaching a pre-determined internalcount value, transmitter 24 transmits a trailing edge at 60 insynchronization signal 54. The length of synchronization signal 54, fromtrigger signal 58 to trailing edge 60, indicates the time base orclocking speed of transmitter 24. In one embodiment, transmitter 24 usesthe indicated time base to transmit data signals 56, which correlatesdata signals 56 to the time base indicated by synchronization signal 54.

Receiver 22 transmits the remainder of request signal 50 after triggersignal 58. The remainder of request signal 50 includes any commandsand/or data to be transmitted to transmitter 24, such as transmitteridentification values, data request parameters such as a sensormeasurement range, configurable parameters such as a relay turn-on/offtime, and commands such as a self-test signal, a wake-up signal, a powerdown signal, a send data and remain powered-up signal, or a send dataand power down signal. Request signal 50 overlaps in time at least aportion of synchronization signal 54 and if receiver 22 and transmitter24 transmit via the same communications path, a trailing edge at 62 inrequest signal 50 occurs before the trailing edge 60 of synchronizationsignal 54 is transmitted via transmitter 24 on the same communicationspath. If receiver 22 and transmitter 24 transmit via differentcommunication paths, the trailing edge 62 of request signal 50 can occurbefore or after the trailing edge 60 of synchronization signal 54 istransmitted via transmitter 24.

In one embodiment, receiver 22 is electrically coupled to transmitter 24via one or more conductive lines and receiver 22 transmits requestsignal 50 on a first conductive line via voltage signals, such asvoltage pulses or voltage bursts. Voltage signals on the firstconductive line is a communications path. Request signal information iscoded into the amplitude and/or length of the voltage pulses or codedinto the amplitude, length, and/or frequency of the voltage bursts.Transmitter 24 transmits reply signal 52 via voltage signals, such as apulse width modulated voltage signal, voltage pulses, or voltage bursts.Where leading and trailing edge information of synchronization signal 54and data signals 56 are coded into the amplitude and/or length of thevoltage pulses or the amplitude, length, and/or frequency of the voltagebursts. Receiver 22 and transmitter 24 generate the voltage signals viasuitable circuitry, such as level-switching power stages, operationalamplifiers, resistor networks, or open-drain/open-collector interfacesincluding pull-ups. Also, receiver 22 and transmitter 24 receive thevoltage signals via suitable circuitry, such as window-detectors,schmitt-triggers, or open-drain/open-collector interfaces includingpull-ups. If transmitter 24 transmits reply signal 52 via the firstconductive line, request signal 50 and reply signal 52 share the samecommunications path and request signal 50 ends before the trailing edge60 of synchronization signal 54. If transmitter 24 transmits replysignal 52 via a second conductive line, request signal 50 and replysignal 52 do not share the same communications path and request signal50 can end before or after the trailing edge 60 of synchronizationsignal 54.

In one embodiment, receiver 22 is electrically coupled to transmitter 24via a conductive line and receiver 22 transmits request signal 50 on theconductive line via voltage signals, such as voltage pulses or voltagebursts. The voltage signals on the conductive line are a firstcommunications path. Request signal information is coded into theamplitude and/or length of the voltage pulses or coded into theamplitude, length, and/or frequency of the voltage bursts. Transmitter24 transmits reply signal 52 via current signals, such as current pulsesor current bursts, where leading and trailing edge information ofsynchronization signal 54 and data signals 56 are coded into theamplitude and/or length of the current pulses or the amplitude, length,and/or frequency of the current bursts. The current pulses on theconductive line are a second communications path, such that requestsignal 50 and reply signal 52 do not share the same communications pathand request signal 50 can end before or after the trailing edge 60 ofsynchronization signal 54.

In one embodiment, receiver 22 is communicatively coupled to transmitter24 via antennae and one or more RF frequencies and receiver 22 transmitsrequest signal 50 via a first RF frequency. The first RF frequency is afirst communications path and request signal 50 is coded into theamplitude, length, and/or frequency of the RF signal or coded into thefrequency/modulation factor, length, or amplitude of an RF modulatedsignal. Transmitter 24 transmits reply signal 52 via an RF frequency,where leading and trailing edges of synchronization signal 54 and datasignals 56 are coded into the amplitude, length, and/or frequency of theRF signal or coded into the frequency/modulation factor, length, oramplitude of an RF modulated signal. If transmitter 24 transmits replysignal 52 via the first RF frequency, request signal 50 and reply signal52 share the same communications path and request signal 50 ends beforethe trailing edge 60 of synchronization signal 54. If transmitter 24transmits reply signal 52 via a second RF frequency, request signal 50and reply signal 52 do not share the same communications path andrequest signal 50 can end before or after the trailing edge 60 ofsynchronization signal 54.

In one embodiment, receiver 22 is communicatively coupled to transmitter24 via an optical coupling, such as LED's or glass fibre, and one ormore wavelengths (color). Receiver 22 transmits request signal 50 via afirst wavelength, which is one communications path. Request signal 50 iscoded into the amplitude, length, intensity, and/or burst frequency ofthe optical signal. Transmitter 24 transmits reply signal 52 via anoptical wavelength, where leading and trailing edges of synchronizationsignal 54 and data signals 56 are coded into the amplitude, length,intensity, and/or burst frequency of the optical signal. If transmitter24 transmits reply signal 52 via the first wavelength, request signal 50and reply signal 52 share the same communications path and requestsignal 50 ends before the trailing edge 60 of synchronization signal 54.If transmitter 24 transmits reply signal 52 via a second wavelength,request signal 50 and reply signal 52 do not share the samecommunications path and request signal 50 can end before or after thetrailing edge 60 of synchronization signal 54.

In one embodiment, receiver 22 is communicatively coupled to transmitter24 via a magnetic coupling, such as a coil, Receiver 22 transmitsrequest signal 50 via the magnetic coupling, which is one communicationspath. Request signal 50 is coded into the amplitude, length, intensity,and/or frequency of the magnetic signal. Transmitter 24 transmits replysignal 52 via the magnetic coupling, where leading and trailing edges ofsynchronization signal 54 and data signals 56 are coded into theamplitude, length, intensity, and/or frequency of the magnetic signal.Request signal 50 and reply signal 52 share the same communications pathand request signal 50 ends before the trailing edge 60 ofsynchronization signal 54.

In one embodiment, receiver 22 is communicatively coupled to transmitter24 via a pressure coupling, such as piezo actor/sensor combinations orloudspeaker/microphone combinations. Receiver 22 transmits requestsignal 50 via the pressure coupling, which is one communications path.Request signal 50 is coded into the amplitude, length, intensity, and/orfrequency of the pressure pulse signal. Transmitter 24 transmits replysignal 52 via the pressure coupling, where leading and trailing edges ofsynchronization signal 54 and data signals 56 are coded into theamplitude, length, intensity, and/or frequency of the pressure pulsesignal. Request signal 50 and reply signal 52 share the samecommunications path and request signal 50 ends before the trailing edge60 of synchronization signal 54.

In other embodiments, receiver 22 and transmitter 24 are suitablycommunicatively coupled. If they share the same communications channelor path, request signal 50 ends before the trailing edge 60 ofsynchronization signal 54. If they do not share the same communicationschannel or path, request signal 50 ends before or after the trailingedge 60 of synchronization signal 54.

In another embodiment of system 20, the synchronization signal istransmitted between data signals. Transmitter 24 starts transmittingdata signals in response to a trigger signal in the request signal.Next, transmitter 24 transmits a synchronization signal and theremainder of the data signals. Some of the data signals are received andstored in receiver 22 prior to receiving the synchronization signal. Thestored data signals are decoded after the synchronization signal isreceived from transmitter 24. Also, at least a portion of the requestsignal overlaps in time at least a portion of the reply signal and oneor more data signals.

In another embodiment of system 20, the synchronization signal istransmitted after the data signals. Transmitter 24 starts transmittingdata signals in response to a trigger signal in the request signal.After transmitting the data signals, transmitter 24 transmits asynchronization signal. The data signals are received and stored inreceiver 22 and decoded after the synchronization signal is receivedfrom transmitter 24. Also, at least a portion of the request signaloverlaps in time at least a portion of the reply signal and one or moredata signals.

FIG. 3 is a diagram illustrating a reply signal 70 that is transmittedvia one embodiment of transmitter 24. Reply signal 70 includessynchronization signal 72, data signal D1 at 74, data signal D2 at 76,and data signal D3 at 78. The data signals D1 at 74, D2 at 76, and D3 at78 include transmitter information, such as transmitter status, data,and checksum information. Each of the data signals D1 at 74, D2 at 76,and D3 at 78 represents one or more data bits. Synchronization signal 72provides a reference time tREF at 72 that indicates the time base oftransmitter 24. Each of the data signal times tD1 at 74, tD2 at 76, andtD3 at 78 correlates to reference time tREF at 72. In one embodiment,each of the data signals D1 at 74, D2 at 76, and D3 at 78 represents anibble of data, i.e. four data bits.

Receiver 22 transmits a request signal (not shown) to transmitter 24 viaone of the communication paths 26. In response to a trigger signal inthe request signal, transmitter 24 provides a falling edge signal at 80and a rising edge signal at 82 in synchronization signal 72. Afterreaching a reference count, transmitter 24 transmits a trailing fallingedge signal at 84. The length of synchronization signal 72, from thefalling edge at 80 to the falling edge at 84 is reference time tREF at72. Synchronization signal 72 is made to be distinguishable from each ofthe data signals D1 at 74, D2 at 76, and D3 at 78. In one embodiment,reference time tREF at 72 is the longest pulse width that can beprovided via transmitter 24. In one embodiment, reference time tREF at72 is the shortest pulse width that can be provided via transmitter 24.

Receiver 22 transmits the remainder of the request signal after thefalling edge at 80. The remainder of the request signal includes anycommands and/or data to be transmitted to transmitter 24. The requestsignal overlaps in time at least a portion of synchronization signal 72.If receiver 22 and transmitter 24 transmit via the same communicationspath, the trailing edge of the request signal occurs before the trailingfalling edge at 84. If receiver 22 and transmitter 24 transmit viadifferent communication paths, the trailing edge of the request signalcan occur before or after the trailing falling edge at 84. In oneembodiment, receiver 22 and transmitter 24 are electrically coupled viaone conductive line and they communicate via open drain/collectortransistors with pull-up resistors, where the remainder of the requestsignal is transmitted after the rising edge at 82 and before the fallingedge at 84.

Transmitter 24 transmits data signal D1 at 74, data signal D2 at 76, anddata signal D3 at 78. The length of data signal D1 at 74, from thefalling edge at 84 to a falling edge at 86, is data signal time tD1 at74. The length of data signal D2 at 76, from the falling edge at 86 to afalling edge at 88, is data signal time tD2 at 76. The length of datasignal D3 at 78, from the falling edge at 88 to a falling edge at 90, isdata signal time tD3 at 78. Each of the data signal times tD1 at 74, tD2at 76, and tD3 at 78 correlates to reference time tREF at 72.

In other embodiments, synchronization signal 72 is transmitted betweenor after data signals, such as data signals D1 at 74, D2 at 76, and D3at 78. The data signals received before synchronization signal 72 arestored and decoded after receiving synchronization signal 72. Also, atleast a portion of the request signal overlaps in time at least aportion of the reply signal and one or more of the data signals.

FIG. 4 is a diagram illustrating one embodiment of an electrical system100, which includes a controller 102, a first sensor 104, and a secondsensor 106. Controller 102 is electrically coupled to each of thesensors 104 and 106 via a 3-wire connection. Controller 102 iselectrically coupled to first sensor 104 and second sensor 106 via VDDpower supply line 108, data line 110, and a reference line, such asground line 112. In one embodiment, system 100 is part of anautomobile's electrical system. In other embodiments, controller 102 iselectrically coupled to any suitable number of sensors.

Controller 102 communicates with first sensor 104 and second sensor 106via open-drain/open-collector interfaces including one or more pull-upresistors. For example, system 100 includes pull-up resistor 114 thathas a first end electrically coupled to power supply line 108 and asecond end electrically coupled to data line 110, and controller 102includes an open-drain transistor 116 that has one end of itsdrain-source path electrically coupled to data line 110 and the otherend electrically coupled to ground line 112. Controller 102 and each ofthe first and second sensors 104 and 106 share a single communicationspath that is communicating via voltage signals on data line 110.

Controller 102 transmits a request signal that is received by the firstand second sensors 104 and 106 via data line 110. The request signalincludes a trigger signal and a sensor identification signal thatselects one of the first and second sensors 104 and 106. In addition,the remainder of the request signal includes any other commands and/ordata to be transmitted to the selected sensor, such as data requestparameters such as a sensor measurement range, configurable parameterssuch as a relay turn-on/off time, and commands such as a self-testsignal, a wake-up signal, a power down signal, a send data and remainpowered-up signal, or a send data and power down signal. Controller 102and each of the first and second sensors 104 and 106 share a singlecommunications path such that the request signal ends before thetrailing edge of the synchronization signal.

The first and second sensors 104 and 106 receive the request signalincluding the trigger signal and the sensor identification signal. Oneof the first and second sensors 104 and 106 is selected via the sensoridentification signal and the selected sensor transmits a reply signalvia data line 110. In one embodiment, the reply signal is similar toreply signal 70 of FIG. 3.

The reply signal includes a synchronization signal and data signals. Thedata signals include sensor information, such as sensor status, sensordata, and checksum information. The length of the synchronization signalprovides a reference time that indicates the time base of the selectedsensor. Each of the data signal lengths correlates to the referencetime. In one embodiment, each of the data signals represents a nibble ofdata, i.e. four data bits.

The request signal and the synchronization signal overlap in time, whereat least a portion of the request signal occurs at the same time as atleast a portion of the synchronization signal. In response to thetrigger signal, the selected sensor starts the synchronization signaland after reaching a reference count transmits the trailing falling edgeof the synchronization signal to mark the end of the synchronizationsignal. The request signal ends before the trailing falling edge of thesynchronization signal.

In one embodiment, the length of the synchronization signal is measuredfrom the trigger signal to the trailing falling edge of thesynchronization signal. In one embodiment, the selected sensor transmitsa falling edge followed by a rising edge to start the synchronizationsignal. In one embodiment, the selected sensor transmits a high voltagevalue at the start of the synchronization signal and the length of thesynchronization signal is measured from the trigger signal to thetrailing falling edge of the synchronization signal. In one embodiment,the length of the synchronization signal is the longest pulse that canbe provided via the selected sensor.

In another embodiment, a data signal is transmitted first in the replysignal, where at least a portion of the request signal occurs at thesame time as at least a portion of the data signal. In response to thetrigger signal, the selected sensor starts the data signal and afterreaching an end count for the data signal transmits the trailing fallingedge of the data signal. The request signal ends before the trailingfalling edge of the data signal.

Controller 102 receives the synchronization signal and measures thelength of the synchronization signal to obtain the time base of theselected sensor. Based on the received time base, controller 102recovers data from the data signals via measuring the length of the datasignals and comparing the measured length to the received time base.

In other embodiments, controller 102 transmits the request signal viaVDD power supply line 108 and first and second sensors 104 and 106transmit reply signals via data line 108.

FIG. 5 is a timing diagram illustrating the operation of one embodimentof system 100 of FIG. 4. Controller 102 communicates with first andsecond sensors 104 and 106 via data line 110. In one communicationsequence, controller 102 selects one of the first and second sensors 104and 106 and the selected sensor provides sensor functions at 130.Controller 102 and the selected sensor transmit data line signal 132 viadata line 110. Data line signal 132 is further described in the logicaldescription at 134.

At 136, first and second sensors 104 and 106 are idle and controller 102transmits a request signal that includes a trigger signal, a sensoridentification signal, and a sensor range signal. The falling edge at138 in data line signal 132 is the trigger signal. The length tID at 140of the low voltage level following the falling edge at 138 and ending ata rising edge at 142 is the sensor identification signal. The length tRat 144 of the low voltage level from the falling edge at 146 to a risingedge at 148 is the sensor range signal.

In response to the trigger signal falling edge at 138, first and secondsensors 104 and 106 start transmitting synchronization signals at 150.In one embodiment, each of the synchronization signals includes afalling edge followed by a rising edge to start the synchronizationsignal. In one embodiment, each of the synchronization signals includesa high voltage level at the start of the synchronization signal.

At 152, each of the first and second sensors 104 and 106 checks the lowvoltage level time tID at 140 of the identification signal. The selectedsensor continues on to check the low voltage level time tR at 144 of thesensor range signal, which indicates the sensor range to use in datatransmissions. Next, the selected sensor transmits a falling edge at 154that ends the synchronization signal of the selected sensor and thesynchronization period 156.

Controller 102 receives the falling edge at 154 of the synchronizationsignal and obtains the time base of the selected sensor. In oneembodiment, the length of the synchronization signal is measured fromthe trigger signal falling edge at 138 to the trailing falling edge at154 of the synchronization signal.

The selected sensor transmits data signals at 158, where each of thedata signals has a length that indicates the bit value of the datasignal. The first data signal at 160 is a status signal that indicatesthe status of the selected sensor. The length of the status signal at160 begins with the falling edge at 154 and ends with a falling edge at162. The length of the second data signal DATA2 at 164 begins with thefalling edge at 162 and ends with a falling edge at 166, and so on, upto the final data signal DATAx at 168 and a checksum signal at 170. Thelength of the checksum signal at 170 begins with a falling edge at 172and ends with a falling edge at 174. At 176, a zero signal begins withthe falling edge at 174 and ends at a high voltage level. The datasignals end at 178 and the selected sensor is idle at 180.

Controller 102 receives the data signals at 158 via data line signal132. Controller 102 measures the length of each of the data signals 158from one falling edge to the next falling. Based on the received timebase, controller 102 recovers the data bit values of each of the datasignals 158.

System 100 provides data communications between controller 102 and firstand second sensors 104 and 106 via the single communications path ofdata line 110. The data communications have a high tolerance to timebase differences between controller 102 and the first and second sensors104 and 106. Also, the request signal and the synchronization signalprovide synchronization of the data communications and the requestsignal provides for the transmission of commands and/or data fromcontroller 102 to first and second sensors 104 and 106. In addition, therequest signal includes sensor identification signals that provide busability.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

1. A system comprising: a receiver configured to transmit a request; anda transmitter configured to transmit a reply signal that at leastpartially overlaps the request.
 2. The system of claim 1, wherein thetransmitter is configured to transmit data in the reply signalcorrelated to a synchronization signal in the reply signal and thereceiver is configured to recover the data based on the synchronizationsignal.
 3. The system of claim 1, wherein the transmitter is configuredto transmit a pulse width modulated reply signal.
 4. The system of claim1, wherein the receiver is configured to transmit a trigger signal inthe request and the transmitter is configured to start the reply signalin response to the trigger signal.
 5. The system of claim 1, wherein thereceiver is configured to transmit the request via one communicationspath and the transmitter is configured to transmit the reply signal viathe one communications path.
 6. The system of claim 5, wherein the onecommunications path is one of a conductive line, an RF frequency, anoptical wavelength, a magnetic signal, and a pressure signal.
 7. Thesystem of claim 1, wherein the receiver is configured to transmit therequest via a first communications path and the transmitter isconfigured to transmit the reply signal via a second communicationspath.
 8. The system of claim 1, wherein the receiver is configured totransmit transmitter identification in the request.
 9. The system ofclaim 1, wherein the receiver is configured to transmit a data requestparameter in the request.
 10. The system of claim 1, wherein thereceiver is configured to transmit a configurable parameter in therequest.
 11. The system of claim 1, wherein the receiver is configuredto transmit a power down signal in the request.
 12. The system of claim1, wherein the receiver is configured to transmit a send data and remainpowered-up signal in the request.
 13. The system of claim 1, wherein thereceiver is configured to transmit a send data and power down signal inthe request.
 14. The system of claim 1, wherein the receiver isconfigured to transmit a self-test signal in the request.
 15. The systemof claim 1, wherein the receiver is configured to transmit a wake-upsignal in the request.
 16. A system, comprising: a receiver configuredto transmit a request; and a transmitter configured to transmit a pulsewidth modulated signal in response to the request, wherein the receiveris configured to receive the pulse width modulated signal.
 17. Thesystem of claim 16, wherein the transmitter is configured to transmit atime base signal in the pulse width modulated signal.
 18. The system ofclaim 17, wherein the transmitter is configured to transmit data in thepulse width modulated signal and the receiver is configured to decodethe pulse width modulated signal and recover the data based on the timebase signal.
 19. The system of claim 17, wherein the time base signaloverlaps the request.
 20. The system of claim 16, wherein the pulsewidth modulated signal overlaps the request.
 21. A system comprising:means for transmitting a request; and means for transmitting asynchronization signal that overlaps the request in time and is inresponse to the request.
 22. The system of claim 21, wherein: the meansfor transmitting a synchronization signal transmits data correlated tothe synchronization signal; and the means for transmitting a requestrecovers the data based on the synchronization signal.
 23. The system ofclaim 21, wherein: the means for transmitting the request transmits therequest via one communications path; and the means for transmitting thesynchronization signal transmits the synchronization signal via the onecommunications path.
 24. The system of claim 21, wherein: the means fortransmitting the request transmits the request via a firstcommunications path; and the means for transmitting the synchronizationsignal transmits the synchronization signal via a second communicationspath.
 25. A method of communicating in a system, comprising:transmitting a request; transmitting a reply signal; and overlapping thereply signal and the request.
 26. The method of claim 25, comprising:transmitting data in the reply signal that correlates to asynchronization signal in the reply signal; and recovering the databased on the synchronization signal.
 27. The method of claim 25,wherein: transmitting the request comprises transmitting a triggersignal in the request; and transmitting the reply signal comprisesstarting the reply signal in response to the trigger signal.
 28. Themethod of claim 25, wherein transmitting the reply signal comprisestransmitting a pulse width modulated reply signal.
 29. A method ofcommunicating comprising: transmitting a request; transmitting a pulsewidth modulated signal in response to the request; overlapping the pulsewidth modulated signal and the request; and receiving the pulse widthmodulated signal.
 30. The method of claim 29, comprising: transmitting atime base signal in the pulse width modulated signal.
 31. The method ofclaim 30, comprising: transmitting data in the pulse width modulatedsignal; and recovering the data from the pulse width modulated signalbased on the time base signal.
 32. The method of claim 30, whereintransmitting a time base signal comprises overlapping the time basesignal and the request.